use same expid for directory and files

Change symbolic link structure to use the same experiment ID for directories and files to facilitate scripting.

Currently it can look like this historical/hist0001/outdata/echam6/hist0001_echam6_BOT_mm_1850.grb It should be like this hist/hist0001/outdata/echam6/hist0001_echam6_BOT_mm_1850.grb

Use the following ids:

• hist

• onepct

• rcp26

• rcp45

• rcp85

• Change create_symlinks.sh

• Make sure to update gather_specific_humidity.sh

mentioned in commit e41aa304

closed via commit b284f31c

marked the checklist item Change create_symlinks.sh as completed

marked the checklist item Make sure to update gather_specific_humidity.sh as completed